A resistively loaded, printed circuit, electrically short dipole element for wideband array applications

In this paper, compact printed ultra-wide band (UWB) antennas with different number of arms are investigated and characterized numerically. As the antennas are proposed to be applied for UWB communication systems such as surface penetrating radar (SPR), they have to provide an ultra-wide band response due to narrow period pulse used by the application. The properties of antennas that are designed to have frequency range of 50–5000MHz for Voltage Standing Wave Ratio (VSWR) less than 2 and size-improved from the preliminary design are characterized with different number of arms and compared each other for some parameters including reflection coefficient (S 11 ), VSWR, gain and radiation efficiency. The optimization for antenna with additional arm is performed in terms of resistive loading application in all ends of arms and adding abrupt transitions onto additional arms. The proposed antennas are designed with 50Ω microstrip line feeding technique and deployed on FR-4 Epoxy substrate with overall size of 50mm × 41.2mm, relative permittivity of 4.3 and thickness of 1.6 mm. From the result, it shows that the proposed antennas achieve good performance i.e. reflection coefficient (S 11 ) < −10dB in the frequency range of 50–5000MHz, where for the mono-arm antenna has a good achievement for lower frequency bands (<1.1GHz) and higher frequency bands (>2.3GHz) whilst for the dual-arm antenna has a good response for pass frequency bands (1.1GHz–2.3GHz). The gain and radiation efficiency of antennas are almost similar each other where the gain of dual-arm antenna as well as radiation efficiency are higher than the mono-arm antenna for frequency ranges higher than 3.5GHz.

In recent years, the UWB technology in wireless communication systems is required for many military, civilian, and medical applications, so small and economic UWB antennas need to be produced for these purposes. Since the Federal Communications Commission (FCC) reported the UWB frequency of 7.5 GHz (from 3.1 GHz to 10.6 GHz) was licensed for high data rate wireless technology and antenna plays a very role in UWB systems. The design, simulation, and fabrication of finger-shaped antenna are presented in this paper. The designed antenna has a reflection coefficient (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) less than -10 dB and voltage standing wave ratio (VSWR) less than 2 for the frequency of 4 to 12 GHz. The far field radiation patterns are introduced with the proposed antenna dimensions and feeding by microstrip transmission line feeder. Simulation and fabrication results for S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> VSWR, radiation patterns, and gain of the proposed antenna are presented and discussed along the frequency band 4 to 12 GHz.

The Kharkiv V. N. Karazin National University MF radar has been widely employed to study mesospheric electrodynamics in the altitude range from 60 to 70 km where the electron density values remain below 100 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . On the other hand, the technique developed at the University for investigating mesospheric electrodynamics demands signal-to-noise ratios greater than five. In addition, a major contribution to signal degradations makes radio interference, and consequently the radar has to operate in a frequency range at the upper end of the medium frequency band, and the antenna array cannot be designed to be resonant. The purpose of this paper is to report the upgrades to the MF radar antenna array to achieve maximum signal-to-noise ratio values. First, the replacement of a point resistive load by a resistor-capacitor load has provided the improvement in the impedance match of the existing antenna to the feeder. The voltage standing wave ratio in the 1.9-3 MHz frequency band could reach 3 before the replacement and does not exceed a value of 1.75 thereafter. Further, the upgrades put forward to the individual antenna arrangement resulted in converting three-lobe antenna pattern only into one-lobe symmetric antenna pattern and low levels of sidelobes over the entire 1.5-3.5 MHz frequency band.

Radio frequency (RF) energy harvester systems are a good alternative for energizing of low-power electronics devices. In this work, an RF energy harvester is presented to obtain energy from Global System for Mobile Communications (GSM) 900 MHz signals. The energy harvester, consisting of a two-stage Dickson voltage multiplier circuit and L-type impedance matching circuits, was designed, simulated, fabricated and tested experimentally in terms of its performance. Simulation and experimental works were carried out for various input power levels, load resistances and input frequencies. Both simulation and experimental works have been carried out for this frequency band. An efficiency of 45% is obtained from the system at 0 dBm input power level using the impedance matching circuit. This corresponds to the power of 450 μW and this value is sufficient for many low-power devices. The most important parameters affecting the efficiency of the RF energy harvester are the input power level, frequency band, impedance matching and voltage multiplier circuits, load resistance and the selection of diodes. RF energy harvester designs should be optimized in terms of these parameters.

The purpose of the work was to study reactions of the immune system with the use of additional respiratory resistance arising from the use of personal respiratory protection. The inspiratory resistance to respiration of 20, 40 and 60% Pmmax was used. The study involved 26 male and female cases at the average age of 21,22,23 years. Based on the results of the study the short-term (3 minutes) effect of inspiratory resistive loads was shown to have a pronounced effect on the population and subpopulation composition of blood lymphocytes, practically without changing the level of secreted immunoglobulins. Different values of additional resistance to respiration were noted to statistically significantly change the level of biogenic amines: the concentration of epinephrine and norepinephrine with elevating values of resistive loads progressively increased; the serotonin concentration shows the opposite dynamics. The work demonstrates the additional respiratory resistance of 20% Pmmax fail to change the immunological status of the subjects. The resistive respiratory load of 40% Pmmax caused immunosuppressive changes in the population composition of lymphocytes and indices of nonspecific immunological resistance. An additional respiratory resistance of 60% Pmmax induced an immunostimulatory effect in the change in the population composition of lymphocytes and in indices of nonspecific immunological resistance. Based on the data obtained, a suggestion has been made that in designing individual respiratory protection devices it is advisable to limit the value of additional inspiratory resistance to respiration of 20% Pmmax.

A compact planar ultra-wideband (UWB) monopole antenna with controllable dual-band-notched characteristics is presented in this paper. U-shaped inverted slot and vertical up C-shaped slot are embedded in the feed line and in the radiating patch, for rejecting WiMAX and WLAN frequency bands, respectively. Moreover, the bandwidth of each rejected band can be independently shifted by adjusting the dimensions of the corresponding band-notched structure. The proposed antenna with two rejected bands characteristics is successfully simulated, prototyped, and measured. The measured results show that the proposed antenna operates until upper 10.6 GHz for voltage standing wave ratio (VSWR) less than 2 and exhibits bands rejection of 3.20–4.1 GHz (24.66%) and 5.20–5.96 GHz (13.62%) frequency band. Furthermore, the proposed antenna shows good radiation characteristics, stable peak gain, and provides more than 80% radiation efficiency, on the entire UWB frequency range except in the notched frequency bands, which prospects the employment in the UWB communication systems.

Ultrawideband (UWB) antenna is one critical part of the impulse radar system. In this paper, a shallow Vee-cavity shielded planar dipole antenna working at the center frequency of 400 MHz for UWB vital sign detection radar is investigated numerically and experimentally. It consists of two half-ellipse-shape arms tuned with four semicircular slots and a shallow Vee-cavity. The voltage standing wave ratio (VSWR), input impedance, and radiation waveforms are all analyzed. The resistive and slot loading techniques for improving impulse radiation and reducing late-time ringing are adopted. Several important parameters of the designed antenna have been studied. The influence of a shallow rectangular cavity and the proposed Vee-cavity on the antenna characteristics is also under consideration. Finally, one prototype antenna is fabricated and applied to UWB vital sign detection radar system. The experimental results indicate that the proposed half-ellipse antenna with a Vee-cavity works satisfactorily in the radar system.

This paper presents the simulation analysis of three dimensional circular embedded patch antenna mounted on coaxial cable for wideband applications. The proposed antenna design is constructed from taking a basic square substrate with ground at lower side which is fed by a cylindrical strip coaxial cable feed line satisfying the 50 Ω requirement. Two vertically symmetrical cylinder of equal diameter with perpendicular to each other are mounted on feed line; which acts as a radiator. High Frequency Structure Simulator (HFSS) is used to analyze the critical parameters and simulation results on the reflection coefficient/return loss, VSWR (voltage standing wave ratio), H-plane, E-plane, gain and radiation pattern of the proposed antenna at various frequencies. The antenna has ability to achieve the frequency range of 3.3–30 GHz along with 160%, 9.09:1 fractional bandwidth and bandwidth ratio (BWR), respectively.

A single stack rectangular dielectric resonator antenna for dual band application is proposed in this paper. The designed antenna is made up of high-temperature withstanding ceramic substrate and mounted on a substrate material of lower permittivity. The antenna is excited by means of an aperture coupled microstrip feeding technique. The proposed antenna operates at two different frequency bands: 2.45 GHz and 3.1 GHz. The antenna is realized using (Finite Elements Method) FEM using ANSYS High Frequency Structure Simulator (HFSS-15.0) software. The designed antenna yields return loss of -42 dB at 2.45 GHz and -19 dB at 3.10 GHz respectively. The other simulated parameters such as radiation pattern, Voltage Standing Wave Ratio (VSWR) and gain over the frequencies of interest are also presented. The proposed antenna is a good candidate of choice to be employed in high-temperature withstanding applications especially for satellite and outer-space applications with peak gain upto 7.30 dB respectively.

This paper designed a circularly polarized (CP) horn antenna working at X frequency band in this paper. The stepped septum polarizer (SP) was used to convert the linear polarization into circular polarization for the discussed square horn antenna. The circularly polarized horn antenna designed in this paper was simulated by using the full wave electromagnetic simulation software, and the specific structure and parameters were provided. The voltage standing wave ratio (VSWR) was lower than 2 within the frequency range of from 8GHz to 8.25GHz. The simulated axial ratio (AR) at the boresight direction at frequency 8GHz was about 3dB. The simulated gains of the designed antenna were about higher than 17dBi within the frequency range of 8GHz to 8.2GHz. The design and simulation results of circularly polarized horn antenna in this paper can provide a reference for the practical engineering application.

This work presents a VCO in the -Gm LC configuration, that operates in the range of 1.3 up to 1.8GHz, followed by amplifiers in the cascode configuration connected to the output. This concept is used with the intention to increase the isolation and inhibits the effects provoked by the impedance mismatches, which depend on the inner and outer agents to the chip. The solution in question inhibits the effects provoked by one of the inner causes of the impedances mismatch, which is the connection with other circuits that are part of a determined system. For the front-ends, the connections with the mixers must be observed with attention, because the VSWR (Voltage Standing Wave Ratio) values, presented by these circuits are high and are between 2.5 and 4.8 in this frequency band. The impedances mismatch effects, caused by wires in the encapsulations assemblies, and in the chip on board, arranged with the output loads are also much minimized to the oscillators, with the amplifiers use in the cascode configuration. The RFIC (Radio Frequency Integrated Circuit) was implemented on SiGe BiCMOS .35μm technology from AMS (Austria Microsystems) foundry.

An electrically small, light-weight, high-efficiency, low-sidelobe Ku-band monopulse Cassegrain antenna with a four-horn feed has been developed for the US Navy's Target Acquisition for Ship Defense Demonstration Program. The authors report the design and performance of a 30-in-diameter (42-wavelength) monopulse Cassegrain antenna. The antenna is protected from the marine environment with a low-loss Teflon feed cover and an epoxy polyamide reflector coating. A simple rectangular four-horn feed with some modification is used to obtain high efficiency and low-sidelobe performance. The design provides 42% overall antenna efficiency in the 15.9-17.1-GHz frequency band (7.3% bandwidth) with better than -19.2-dB sidelobes at the nominal frequency. The voltage standing wave ratio at the sum and difference ports is better than 1.7 for the entire frequency band. The measured performance data are summarized, and some representative measured patterns are shown. >

The letter presents a low‐windage omnidirectional antenna for high‐speed aircraft in the UHF and L bands. It combines a planar biconical antenna with a printed tape parasitic branch monopole antenna. Upgrading the traditional restricted‐length biconical antenna to a double‐layer planar design meets the compact, lightweight, and low windage requirements of airborne use. To enhance bandwidth and meet the lightweight, compact criteria of high‐speed aircraft, the planar‐printed monopole antenna integrates parasitic stubs and loop antenna concepts. Experimental results exhibit excellent isolation between antenna elements, with over 15 dB segregation and operational spectrum return loss of 27% and 18% at 10 dB. The voltage standing wave ratio is below 2, with less than 5 dB variation in the horizontal radiation pattern across frequency bands. The antenna, measuring 20 mm × 190 mm × 270 mm and weighing around 0.5 kg, holds great promise for high‐speed aircraft applications.

An S-band dual circular polarizer has been designed and tested with low power in the paper, which will be applied in a spherical cavity pulse compressor. It converts the TE $$_{10}$$ mode in rectangular waveguide into two polarization degenerated TE $$_{11}$$ modes in cylindrical waveguide. The general scattering matrix of the dual circular polarizer has been deduced based on the properties of the passive microwave network, which is suitable for the usual 3 dB coupler, as well as the left/right hand circular polarizer. Based on the 3D code software CST, the dual circular polarizer was numerically simulated. Then, two prototypes have been manufactured and tested with the vector network analyzer (VNA). The simulation results show that the magnitudes and phase difference of the two TE $$_{11}$$ modes are − 3.0103/− 3.0104 dB and 89.79 degrees, respectively. The cold test results show good agreement with CST simulation. The method of analyzing the relationship between the voltage standing wave ratio (VSWR) and the errors of the magnitudes and phase difference of the two TE $$_{11}$$ modes was given, which can be used to qualitatively analyze the properties of the circular polarizer. The S-band waveguide dual circular polarizer can be applied in the pulse compressor, phase shifter or other frequency bands.

A compact coplanar waveguide (CPW)-fed circular slot ultrawideband (UWB) antenna with dual-band filtering characteristic is presented in this article. The dual-band filtering characteristic is achieved by inserting an arc-rectangle-shaped stepped impedance resonator in the circular ring radiation patch and etching a spiral stepped impedance resonator in the CPW-fed transmission line. The numerical and experimental results demonstrate that the proposed antenna can operate on a frequency band between 2.7 and 12 GHz with voltage standing wave ratio less than 2, except for that two filtering bands between 4.8 and 6 GHz and between 7.6 and 8.6 GHz are used to prevent the potential interference from WLAN band and X-band. In addition, the proposed antenna has a compact size and omnidirectional radiation pattern, which is suitable for UWB communication applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:925–929, 2014